Thermionic valve circuits



Sept. 24, 1%35. w wg s 2,015,506

THERMIONIC VALVE CIRCUITS Original Filed Sept. 21, 1923 INVENTOR P. W. WILL NS BY 1 J W &TTO RNEY Patented Sept. 24, 1935 UNITED STATES THERMIONIC VALVE CIRCUITS Peter William Willans, Towcester, England, assignor to Radio Corporation of America, a corporation of Delaware Application September 21, 1923, Serial No. 663,986

Renewed June 24, 1932.

October 4, 1922 4 Claims.

This invention relates to thermionic valve amplifying circuits.

In order to ensure faithful reproduction of speech it is frequently necessary to apply a high 5 negative voltage to the grid of a valve and in other cases also it is frequently of advantage to apply a negative potential to the grid of a valve used for amplifying.

According to this invention I apply negative potential to the grid of an amplifying valve by inserting in the anode circuit between the filament and the negative terminal of the high tension battery a resistance the voltage drop along which due to the anode current furnishes the negative voltage required, and I connect the grid to any suitable point in this resistance. The resistance is shunted by a condenser of large capacity to bypass the alternating current. Another condenser may be inserted across the filament and grid.

My invention is illustrated by the single figure of the accompanying drawing which is a diagrammatic representation of a circuit embodying the invention. In the drawing a two valve speech amplifier is shown by way of example, A, B, are the two valves having a common high tension battery C; between the negative terminal of this battery and the negative ends of the filaments of the valves is inserted a resistance D to which the grids of the valves are connected by tap-s E, El, which are preferably adjustable. By adjusting these any required negative voltage can be sup-plied to the grids and the characteristics of the respective valves varied thereby. The resistance D is shunted by a condenser F which should be. of such a capacity that its impedance for the frequency at which the amplifier works is small in comparison with that of the resistance. If preferred the condenser may shunt the battery C as well as the resistance D.

Having described my invention what I claim 1. An amplifying system including a plurality of three electrode tubes each comprising an anode, a cathode and a control electrode, a circuit connecting the anode and cathode of each tube including a direct current source of energy and a resistance in series common to all tubes, means for connecting the control electrodes of each tube to points on the resistance, and a by-pass condenser shunting said resistance and energy source, said condenser being adapted to by-pass high frequency currents.

2. An amplifying system including a plurality of three electrode tubes each comp-rising an anode, a cathode and a control electrode, a circuit for each tube connecting its anode to its cathode, a direct current source of energy common to all of said circuits, a resistance common to said cir- In Great Britain cuits connected between the negative terminal of said source and the cathodes of said tubes, a bypass condenser shunting said resistance and energy source, said condenser being adapted to bypass high frequency currents and means for adjustably connecting the control electrodes of said tubes to points on said resistance.

3. In combination, a pair of electron discharge tubes each thereof having anode, cathode and control electrodes, said electrodes cooperating to form input and output circuits for each of said electron tubes, a power supply circuit for said tubes comprising a current source, a resistance element and a condenser all three forming a series closed circuit, direct current being prevented from traversing said circuit by said condenser, means forincluding said resistance element and current source in both output circuits and means for including variable portions of said resistance element in at least the input circuit of one of the tubes for applying a variable negative bias to the grid of the tube whereby the amplification characteristics of the tube may be varied as desired.

l. In an amplifier circuit a space discharge de vice having an input circuit including a grid electrode and a cathode and an output circuit including an anode and said cathode, means for impressing signal pulsations upon said input circuit, a second space discharge device having an input circuit including a grid electrode and a cathode and an output circuit including an anode and said cathode, the output circuit of said first mentioned space discharge device being coupled to the input circuit of said second named space discharge device, an energizing source for both of said space discharge devices having a positive terminal and a negative terminal, means for connecting both of said anodes to the positive terminal of said source, a connection including a resistance element connected between the cathode and grid electrode of said first named space discharge device, means for passing current therethrough so as 00 bias the grid of said first named space discharge device negatively with respect to the cathode thereof and manually operative means to control the negative bias on the grid thereby varying the operating characteristics of said first named space discharge device whereby the amplitude of pulsations transferred from the output circuit of the first named space discharge device to the input circuit of the second named space discharge device through said coupling resulting from pulsations impressed upon the input circuit of the first named space discharge device may be controlled and a capacitive path of low impedance to the signal energy shunted across both the resistance and the energizing source.

PETER WILLIAM WILLAN S. 

